It is known for an underwater vehicle, which is towed and not self-propelled, to carry a sonar sensor, such as for mapping the ocean floor. Sometimes a heavy tow cable, dead weight depressor and/or dynamic-lift depressor is required to achieve the desired depth of the towed vehicle. Also, heave (up and down motion) and surge (back and forth motion) of the towing vehicle can result in the tow line erratically pulling the towed vehicle, so that the towed vehicle does not travel steadily and the sonar data is obtained under fluctuating conditions. It is known to decrease the speed of the towing vehicle in an effort to cause the towed vehicle to travel more steadily, but decreasing the speed can increase the amount of time that is required to obtain the sonar data and can increase the amount of heave transferred to the towed vehicle.
Accordingly, there is a need for a towable vehicle that provides a new balance of properties.